Tissue Expander Capsule as an in Vivo Bioreactor to Construct Axial Pattern Buccal Mucosa-Lined Flap for Tubularized Urethral Reconstruction: Preliminary Results in an Animal Model

Background: Tubularized buccal mucosa (BM) graft urethroplasty fail largely because of inadequate graft take and prefabrication of BM-lined flap has theoretical indications for constructing neourethra with independent blood supply. The efficacy of a prefabricated BM-lined flap for tubularized urethral reconstruction was tested. Methods: Tissue expanders were used for vascularized capsule induction. Autologous buccal mucosa graft were transplanted to the capsule pouch for evaluation. A circumferential urethral defect was created and tubed urethroplasty was performed with buccal mucosa graft (8 rabbits, group 1), capsule flap (8 rabbits, group 2) and the prefabricated capsule-buccal mucosa composite flap (8 rabbits, group 3). At 1 and 3 months after urethroplasty, retrograde urethrography and histological analyses were performed to evaluate the results of urethroplasty. Findings: The mucosa showed complete survival on the vascularized capsule and was expanded by the tissue expansion process. Under retrograde urethrography, none rabbits in group 1, 3 rabbits in group 2 and 6 in group 3 maintained a wide urethral caliber. Histologically, part of the tubed buccal mucosa graft survived in the neourethra. In group 2, discontinued epithelial layer regenerated at 1 month and the constructed neourethra narrowed even though the lumen surface formed intact urothelial cells at 3 months. In group 3, buccal mucosa formed the lining in the neourethra and kept a wide urethral caliber for 3 months. Interpretations: The capsule may serve as an in vivo bioreactor for buccal mucosa-lined flap prefabrication. The prefabricated buccal mucosa-lined flap could be used for tubularized urethral reconstruction. Funding: This study was supported by grants from the National Natural Science Foundation of China (81470911) and the Ph.D. Candidate Innovation Fund of Shanghai Jiao Tong University School of Medicine (BXJ201741). Declaration of Interest: The author declared no potential conflicts of interest with respect to the research, authorship, and publication of this article. Ethical Approval: The whole animal experimental protocol was approved by the Animal Care and Use Committee of Shanghai Jiao Tong University School of Medicine.